Vehicle emission control systems may be configured to store refueling vapors, and in some examples running-loss vapors and diurnal emissions in a fuel vapor canister, and then purge the stored vapors during a subsequent engine operation. The stored vapors may be routed to engine intake for combustion, further improving fuel economy for the vehicle. In a typical canister purge operation, a canister purge valve (CPV) coupled between the engine intake and the fuel vapor canister is opened or duty cycled, allowing for intake manifold vacuum to be applied to the fuel vapor canister. Fresh air may be drawn through the fuel vapor canister via an open canister vent valve. This configuration facilitates desorption of stored fuel vapors from the adsorbent material in the canister, regenerating the adsorbent material for further fuel vapor adsorption.
Such fuel vapor canisters may in some examples include a canister filter configured to filter carbon dust and other particulate matter from air and fuel vapor during a canister purging operation, prior to the air and fuel vapor being routed to the engine. In this way, degradation of one or more of the CPV, intake and/or exhaust valves of engine cylinders, etc., may be reduced or avoided. However, over time the canister filter may become restricted or clogged to varying extents. As the canister filter becomes increasingly more clogged, engine manifold vacuum may be restricted in its ability to purge the canister. Inability to purge the canister may lead to aborted canister purging operations, and may result in the canister becoming saturated with fuel vapors which may lead to an increase in release of undesired evaporative emissions to atmosphere. A clogged canister filter may further impede particular evaporative emissions diagnostics that rely on evacuation of the vehicle fuel system and/or evaporative emissions system. The inventors have herein recognized the above-mentioned issues.
U.S. Pat. No. 9,599,071 discloses a canister filter diagnostic that relies on a pump disposed in a vent line between a canister and atmosphere to reduce a pressure of an evaporative emissions system to a reference pressure. Therein, in response to a time frame for reaching the reference pressure being less than a threshold duration, a canister restriction is indicated.
However, the inventors have herein recognized potential issues with such a method. Specifically, such a method relies on a pump being included in the vent line of the evaporative emissions system, along with one or more pressure sensors positioned in the evaporative emissions system and/or fuel system. Certain vehicles may not be equipped with such a pump and/or the one or more pressure sensors, and thus may be unable to ascertain the extent of canister filter clogging via the methodology of U.S. Pat. No. 9,599,071.
Accordingly, the inventors have herein developed systems and methods to at least partially address the above-mentioned issues. In one example, a method comprises diagnosing an extent to which a canister filter coupled to a fuel vapor storage canister positioned in an evaporative emissions system of a vehicle is clogged based on an output of an exhaust gas sensor positioned in an exhaust passage of an engine, and adjusting one or more parameters related to purging of the fuel vapor storage canister as a function of the extent to which the canister filter is clogged. In this way, the extent to which the canister filter is clogged may be inferred without reliance upon a pump or pressure sensor(s) positioned in the vehicle fuel system and/or evaporative emissions system.
In one example, diagnosing the extent to which the canister filter is clogged may be based on a time duration between initiation of a purging event of the fuel vapor storage canister and the output of the exhaust gas sensor. The output of the exhaust gas sensor may comprise an indication of a rich air-fuel ratio, for example. Diagnosing the extent to which the canister filter is clogged may be based on a time duration between initiation of a purging event of the fuel vapor storage canister and the output of the exhaust gas sensor, for example. The extent of canister filter clogging may be inferred based on a comparison between the time duration and a baseline time duration, the baseline time duration obtained under conditions where the canister filter is new and thus not clogged to any appreciable extent. By regularly inferring the extent of canister filter clogging, remaining canister filter lifetime may be inferred, purging operations may be improved, and release of undesired evaporative emissions to atmosphere may be reduced or avoided.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.